Mechanical shutter for iris in which shutter blade edge moves while remaining parallel to electric field



Jan. 21, 1964 D. w Foss 3,119,083

MECHANICAL SHUTTER FOR IRI IN WHICH SHUTTER BLADE EDGE MOVES WHILE REMAINING PARALLEL TO ELECTRIC FIELD Filed Oct. 11, 1960 FIG. 2

26 IFIG. 1

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DAVID w. FOSS BYgj yz ATTORNEY United States Patent O 3,119,083 MECHANICAL SHUTTER FOR IRIS IN WHICH SHUTTER BLADE EDGE MDVES WHILE RE- MAININ G PARALLEL TO ELECTRIC FIELD David W. Foss, Beverly, Mass., assignor, by mesne assignments, to Varian Associates, Palo Alto, Calif., a corporation of California Filed Get. 11, 1960, Ser. No. 62,023 7 Claims. (Cl. 333-83) The present invention relates generally to microwave transmission devices and in particular to cavity resonators coupled to associated waveguide transmission systems.

In the microwave transmission field it is desirable in certain applications to control the power transmitted from .a source of low power electromagnetic energy, such as a klystron while at the same time stabilizing the operating frequency. Prior art structures comprise high Q cavity resonators coupled by means of iris openings to associated waveguide systems to provide the output path for the electromagnetic energy generated by a conventional source. One example of a low power source of energy is the reflex type klystron oscillator wherein power output may be partially controlled by adjustment of the anode voltages. Such a power controlling or adjustment technique is limited in magnitude of power that can be altered; requires an associated change of reflector voltages; and produces undesirable frequency changes particularly when power of the order of 100 mill-iwatts must be reduced to the order of 1 milliwatt for feeding an intermediate frequency mixer in conventional microwave system usage.

The present invention has :for its principal object the provision of improved power controlling apparatus to be incorporated directly in a microwave cavity resonator. A further object is to provide an improved power controlling apparatus for a microwave transmission system which is superior in performance to prior art apparatus. Another object is to provide in an iris coupled microwave cavity resonator an integral power output control apparatus without any resultant change of the desirable electrical characteristics of said resonator.

The realization of the foregoing objects is attained by means of a power controlling member communicating with an iris opening in the side wall of a microwave cavity resonator. Disposal of the controlling member across the opening to control thereby selectively the power output has successfully resulted in attenuation values in excess of 30 decibels of transmitted energy. The resonant frequency and the voltage standing wave ratio of a selected resonator were only minutely afiected while the electrical reference plane location of the output section of the resonator remained substantially unaltered in comparison with prior art power controlling apparatus.

Additional objects and advantages will be evident after consideration of the ensuing full and complete detailed discussion of a selected embodiment together with references to the accompanying drawings, in which:

FIG. 1 is a side elevation view with a portion of the cavity resonator adjacent to the output end broken away to disclose internal structure;

FIG. 2 is a front elevation view taken along the line A-A in FIG. 1.

Referring to the drawings, FIG. 1 illustrates a cavity resonator I mounted between associated waveguide sections 2 and 3. Waveguide 2 will be referred to as the input section and is provided with a mating flange 4 for coupling any suitable source of microwave electromagnetic wave energy such as for example a reflex-type klystron oscillator tube. Another flange 5 is provided 3,119,083 Patented Jan. 21; 1964 ice for mounting the waveguide section to the cavity resonator body. In like manner, the energy propagated through the cavity resonator is coupled to a waveguide transmission system by means of output section 3 having flanges '6 and 7 disposed at the ends thereof. A plurality of screws 8 secure flanges 5 and 7 to the cavity resonator body.

The cavity resonator 1 may be of the conventional type employed in microwave transmission systems for numerous purposes, including stabilization of the frequency fed into the intermediate frequency circuit to convert ultra high frequency energy into discernible information. In the illustrative embodiment the resonator 1 has been shown as a cylinder with its axis perpendicular to the axis of the waveguide sect-ions 2 and 3. Such arrangement is incidental to a particular electromagnetic energy mode selected and is by no means intended as a limitation of the invention.

To facilitate transmission of electromagnetic energy within a selected microwave frequency range, wave permeable window members 9 and 10 will be provided at diametrically opposite points in the resonator body wall 11 in alignment with the waveguide sections 2 and 3. Iris openings 12 and 13, preferably of circular configuration, are provided in the Wall 11. Each window member comprises a frame member 14 and a dielectric member 15 to thereby enclose and hermetically seal the cavity resonator. Window member 9 is mounted within a recess 16 in resonator wall 11 and a flat surface 17 is milled in the curved surface of the cylinder to provide a mating surface for flange 5.

Opposing window member '10 is mounted in a reverse manner so as to be disposed inwardly. To this end an insert 18 with the window member mounted in a recessed portion 19 may be sub-assembled and then solder-ed within the resonator wall as at 20. The insert is contoured as at 21 to match the inner wall configuration of the cavity resonator. It is an important feature of the present invention that the output window member be so mounted as will be evident from the ensuing description of the preferred embodiment.

in accordance with the teachings of the present invention the coupling of low power electromagnetic wave energy from a suitable generator is selectively controlled by adjusting the dimensions of iris opening 12 by means of a movable vane member 22. It is noted that the movable vane member 22 is secured within its supporting structure adjacent the iris opening 12 such that the vane member 22 extends across the iris opening in a direction taken from one broad wall of the waveguide 3 toward the mutually opposed broad wall of the waveguide. The vane member 22 is movable in a direction transverse to the plane of the narrow side walls of the guide and substantially parallel to the broad side walls of the guide to close off the iris 12. When the is closed in this manner the iris is efiectively variably shorted such that the coupling through the iris is reduced in proportion to the remaining area of the iris. The supporting structure for the vane member 22 comprises a semi-circular member 23 brazed to the upper part of flange 7 and defining therein a raceway 24. A locking screw 25 milled on two parallel sides to a flat surface is secured to an end of vane member 22 and extends through raceway 24. Lock nut 26 secures the vane member in its desired position after adjustment of output power. A pivot pin 27 secured to the resonator body wall provides for gradual extension of the vane member across the face of opening 12 in a semi-circular path to thereby control the power output.

Dotted lines 28 indicate the boundaries of a slot milled in flange 7 to receive the vane member when flange 7 is '3 contacting the outer flat surface of insert 18 and adjacent resonator wall structure which is also milled flat. It is necessary for the eflicient operation of the vane member that all the surfaces adjacent to the opening 12 be contacted at all times the adjustment of the disposition thereof in the path of the electromagnetic energy.

A phase adjusting screw 25 in lwaveguide section 2 may be desired in certain applications and a similar screw (not shown) may also be provided in accordance with conventional practice in the art.

Many variations from the specifically described apparatus may be envisaged by skilled artisans without departing from the spirit and scope of the invention. It is to be understood that this description of the invention shall be interpreted as exemplary and not in a limiting sense in conformity with the definition thereof in the appended claims.

Having thus described the invention, I claim:

1. In combination, a cavity resonator structure, a hollow substantially rectangular waveguide structure coupled to said cavity, said cavity resonator having a coupling aperture in a wall thereof in registry with said hollow waveguide for coupling wave energy between said cavity and said waveguide, said hollow rectangular waveguide defined by a pair of mutually opposed spaced apart substantially planar broad walls and a pair of mutually opposed spaced apart substantially planar narrow walls, means communicating with said coupling aperture for controlling the passage of wave energy between said waveguide and said cavity, said controlling means comprising a metallic member disposed across said aperture in a direction from one broad wall of said guide toward the other opposed broad wall, and means for moving said metallic member across said aperture in a direction substantially transverse to the plane of said'narrow walls and generally parallel to the plane of said broad walls of said waveguide.

2. The apparatus according to claim 1 wherein said hollow substantially rectangular waveguide structure includes a pair of hollow rectangular iwaveguide sections disposed on opposed sides of said cavity and communicating with said cavity via the intermediary of a pair of coupling apertures disposed in registry with said waveguide structure.

3. The apparatus according to claim 2 including a pair of gas tight dielectric wave permeable window members sealing off said pair of coupling apertures and forming a portion of a gas tight envelope of said resonator, low power electromagnetic Wave energy generating means coupled to one section of said waveguide structure, and said metallic member being pivotably mounted to swing across one of said coupling apertures.

4. The apparatus according to claim 2 wherein one of said wave permeable window members is disposed 'within the interior of said cavity resonator, said metallic member being pivotably mounted on an external wall of said cavity resonator structure adjacent said coupling aperture having the interiorly disposed window member.

5. The combination as claimed in claim 1 wherein said metallic member contacts all wall surfaces adjacent to said aperture.

6. The combination as claimed in claim 4, wherein the width of said metallic member exceeds the width of the aperture.

7. The combination as claimed in claim 4, and means for securing the metallic member in the predetermined position disposed at the outer end thereof.

References Cited in the file of this patent UNITED STATES PATENTS 2,375,223 Hansen et al May 8, 1945 2,423,130 Tyrrell July 1, 1947 2,544,715 Muchmore Mar. 13, 1951 2,545,472 Kline Mar. 20, 1951 2,549,721 Strauss et a1 Apr. 17, 1951 2,584,717 Alpert Apr. 5, 1952 2,703,886 De La Cova et al Mar. 8, 1955 OTHER REFERENCES Ragan: Microwave Transmission Circuits, pages 219 and 22 0, McGraw-Hill Book Co., Inc., New York, N.Y., copyright 1948. 

1. IN COMBINATION, A CAVITY RESONATOR STRUCTURE, A HOLLOW SUBSTANTIALLY RECTANGULAR WAVEGUIDE STRUCTURE COUPLED TO SAID CAVITY, SAID CAVITY RESONATOR HAVING A COUPLING APERTURE IN A WALL THEREOF IN REGISTRY WITH SAID HOLLOW WAVEGUIDE FOR COUPLING WAVE ENERGY BETWEEN SAID CAVITY AND SAID WAVEGUIDE, SAID HOLLOW RECTANGULAR WAVEGUIDE DEFINED BY A PAIR OF MUTUALLY OPPOSED SPACED APART SUBSTANTIALLY PLANAR BROAD WALLS AND A PAIR OF MUTUALLY OPPOSED SPACED APART SUBSTANTIALLY PLANAR NARROW WALLS, MEANS COMMUNICATING WITH SAID COUPLING APERTURE FOR CONTROLLING THE PASSAGE OF WAVE ENERGY BETWEEN SAID WAVEGUIDE AND SAID CAVITY, SAID CONTROLLING MEANS COMPRISING A METALLIC MEMBER DISPOSED ACROSS SAID APERTURE IN A DIRECTION FROM ONE BROAD WALL OF SAID GUIDE TOWARD THE OTHER OPPOSED BROAD WALL, AND MEANS FOR MOVING SAID METALLIC MEMBER ACROSS SAID APERTURE IN A DIRECTION SUBSTANTIALLY TRANSVERSE TO THE PLANE OF SAID NARROW WALLS AND GENERALLY PARALLEL TO THE PLANE OF SAID BROAD WALLS OF SAID WAVEGUIDE. 